Method of producing lubricating oil



Jan. 24, 1939. 1 D. FULTON Er A1.

METHOD OF' PRODUCING LUBRICATING OIL Filed March 9, 1957 Patented Jan. 24, 1939 UNITED STATES METHOD F PRODUGING LUBRICATING OIL Luther D'. Fulton, Titusville, and Joseph M. Hinman, Rouseville, Pa.,

assignors to The Pennzoil Company, Oil City, Pa., a corporation of Pennsylvania Application March 9,

9 Claims.

This invention relates to a method of producing lubricating oil from petroleum.

In the production of bright stock which is to be blended with a neutral oil to provide a lubricating oil it is the practice to add a light diluent to the cylinder stock or other oil from which the bright stock is to be produced in order to obtain a solution of the desired specific gravity. The solution thus produced is chilled to precipitate the amorphous wax and thereafter centrifugalized or otherwise treated to remove the said wax, or petrolatum as it is commonly called, the chilling being carried out at a predetermined low and uniform rate in order that the wax will be p-recipitated in such a state that its separation can be eiected economically enough to be commercially feasible. As a result of the cooling of the solution in the manner described a substantialquantity of the oil is occluded by the petrolatum. The constituents of the oil which is occluded are for the most part those which, owing to their chemical structure have an affinity for the congealing wax particles, being in the nature of homologues of the wax. These constituents, we have discovered, have a viscosity and a viscosity index which are much higher than those of the remaining oil constituents. Their removal from the solution with the wax, therefore, is not only objectionable because of 30 the lower yield but is also objectionable as a result of the lowering of the viscosity and viscosity index of the bright stock produced by fractionation of the solution, and hence of the lubricating oil produced by blending the said stock with a neutral.

The principal object of the present invention is a process which does not have the above objec'tions and which, therefore, will enable the production of a lubricating oil having a high 4,0 viscosity index, this object contemplating the recovery and utilization of those constituents which, heretofore, have been lost as an incident to the dewaxing of the bright stock.

A still further object is to provide a process which will enable the production of a high viscosity index lubricating oil having low cloud and pour points.

Apparatus for carrying out the method is illustrated diagrammatically in th-e accompanying drawing.

In the practice of the invention an oil distillate, petrolatum and a light diluent such as naphtha are blended in a tank I, the proportions of the said components being fixed by the viscosity of the oil which is to be produced. For example, if a lubricating oil of S. A. E, l0 viscosity is to be produced and a dewaxed re-run distillate (neutral oil) is employed the neutral oil, naphtha and petrolatum should be in the approximate proportions 30%, 62% and 8%, re-

1937, Serial No. 129,878

spectively. The blend may be produced, if det sired, by addingl petrolatum from which the naphtha has been distilled to the neutral oil and heating the said components to a temperature of the order of 300 F., the naphtha in this case being added after the components have been cooled to a suitable temperature; or a petrolatum solution containing naphtha may be added to the neutral at a temperature below the flash point of the solution, additional naphtha then being added to suitably dilute the blend; or the blend may be produced by dissolving the petrolatum in -naphtha at a temperature somewhat less than the vaporization point of the diluent, the neutral then b-eing added. As shown, and preferred, however, the petrolatum which is introduced into the tank l is a solution which is produced by a centrifuge 2, the other product of the centrifuge being a dewaxed bright stock solution. The original solution introduced into the said centrifuge is cylinder stock or any other suitable oil and naphtha. The latter is preferably 60% to '70% by volume of the solution, the separation of the components of the cylinder stock being regulated so that enough bright stock is carried over with the petrolatum solution as will produce, with the neutral, an -oil of the desired viscosity.

The neutral, or other distillate, which is introduced into the tank l may be produced in any suitable manner. As illustrated, a wax distillate cut from the primary distillation of crude oil is chilled in a tank 3 to precipitate the crystalline Wax and is conducted to a filter press 4 in which the said Wax is removed, it being understood that the greater the percentage of such wax which is removed the higher will be the solubility characteristic of the distillate. For example, if all of the wax with the exception of approximately .2% or less, is removed a distillate is provided which is highly effective for the purpose in view. The pressed distillate is then heated to a suitable degree in a heater 5 and introduced into a fractionating tower B in which the gas oil is removed. The neutral oil thus produced may be solvent treated, if desired, to remove the undesirable impurities. It is to be understood that, if preferred, the dewaxed distillate from the iilter press i may, without further treatment, be introduced directly into the blending tank l instead of the neutral oil.

To the petrolatum solution and neutral oil in the tank i additional naphtha from the tank 'l is added to bring the naphtha content up to the desired value. The temperature of the solution is then raised to approximately 110 F. or to a temperature between such value and that at which the diluent vaporizes, whereby to render soluble the Wax constituents. Preferably the heated solution is agitated to insure a thorough and intimate mixing of the components.

The invention contemplates a low temperature fractionation of the solution which is blended in the tank I. To this end the said solution is caused to ow successively through a series of tanks 8, 9, I0 and II wherein its temperature is reduced in stages to a temperature Within the range of 42 F. to 79 F., preferably a temperature of the order of 58 F. In tank 8 the first stage of chilling is effected, the temperature of the solution being lowered at a rate of the order of 9.8 F. per hour to approximately 32 F., and hence to a value below that at which crystallization of the Wax begins. The second stage of chilling is carried out in the tank 9, the temperature of the solution being lowered further in the said tank at substantially half the rate, or 4 F. per hour, as in the first stage, to approximately 8 F. In the second stage a substantial portion of the wax is precipitated. At the same time those constituents having a high viscosity and a high viscosity index and which are of the nature of homologues of the amorphous Wax enter into solution with and are assimilated by the neutral oil, being replaced, it is believed, by constituents of high molecular weight and low viscosity index originally present in the neutral oil. The solution is subjected to a third stage of chilling in tank I0. In this stage the solution is shock chilled, being reduced in temperature at substantially the same rate as in the first stage, or approximately 8.3" F. per hour, to a temperature of a value of the order of 42 F. The rapid chilling of the solution at this stage causes the remaining wax to precipitate in fine crystals which may be thoroughly washed by the neutral oil, thereby preventing occlusion of the high viscosity and high viscosity index constituents which are in solution with the neutral oil at this time. In this stage complete crystallization of the wax is effected including a substantial part of the small percentage of crystalline Wax originally present in neutral oil. The fourth stage of chilling occurs in tank I I, the solution being lowered in temperature at this stage at approximately one-fourth the rate of the first stage, or 2.7 F. per hour, to a value of the order of -58 F. In this stage certain of the high molecular weight hydrocarbons of low viscosity index are maintained at a temperature which renders them wholly, or to a large part, insoluble in the neutral oil and naphtha. The third and fourth stages are illustrated and described as independent and separate stages. This is preferred as the chilling of the solution in the fourth stage may be regulated to balance fluctuations in the preceding stages. It is to be understood, however, that a single chilling stage may be substituted, if desired, for the third and fourth stages by suitably increasing the capacity of the chilling tank employed for this purpose.

I'he solution which has been chilled in the manner described is then treated to separate the precipitated wax and those high molecular weight and low viscosity index constituents which are in a solid or semi-solid state. The separation of the said constituents may be effected by a lter press or may, as illustrated, be accomplished by a centrifuge I2. When the latter is employed the wax and other solids are removed in the form of a slurry. The cold lubricating oil solution remaining is deliVerd by a pump I2a to the tank 8 and caused to flow, counter-current, in heat exchange relation with respect to the hot blend from the tank I. It is then heated to a suitable temperature in a heater I3 and introduced into a fractionating tower I4 in which the diluent is driven off, the final product being lubricating oil of the desired viscosity. The lubricating oil thus produced contains those constituents having a high viscosity and a high viscosity index which were originally occluded by the petrolatum and which, under present practice, would be lost during the production of the bright stock. The lubricating oil, therefore, has a higher viscosity index than oil produced by conventional methods. A further advantage obtained is that the oil has low cloud and pour points of substantially the same value.

The slurry solution separated by the centrifuge I2 contains fractions of the neutral oil having high viscosity index characteristics. It is preferred, therefore, that the said solution be conducted to a heater I5 in which its temperature is raised to a suitable degree. Thereafter it is introduced into a fractionating tower I6 in which separation of the diluent and the bottoms is effected. The fractions of neutral oil which are to be recovered are taken oi in an intermediate cut as a wax bearing distillate. They are conducted to a tank I1 in which they are chilled to precipitate the wax and then introduced into a filter press I8 in which the wax is removed, the dewaxed distillate being returned to the blending tank.

From the foregoing it will be apparent that the production of a lubricating oil in accordance with the invention involves the recovery from petrolatum of those constituents of high viscosity and high viscosity index which, heretofore, have been lost in the production of the bright stock. In the attainment of the ends of the invention the petrolatum (including the proper proportion of bright stock) is blended with the neutral oil in a suitable diluent at a temperature adequate to render soluble the wax constituents of the blend. In the subsequent low temperature fractionating operations the constituents having high viscosity and high viscosity index and originally occluded by the amorphous Wax in the petrolatum are assimilated by and held in solution with the neutral oil while the naphtha holds the neutral and the said constituents in Solution. In other Words, the neutral serves as a diluent for the constituents of high viscosity and high viscosity index while the naphtha., also serving as a diluent, holds the neutral in solution. The solution thus provided may, therefore, be chilled to precipitate the wax in such a manner as to prevent occlusion of the constituents of high viscosity and high viscosity index, it being noted that in all stages the chilling rate is maintained at a value in excess of two degrees per hour. The recovery of the constituents of high viscosity and high viscosity index, therefore, improves the lubricating oil qualitatively and enables a higher yield than would otherwise be obtained.

We claim as our invention:

l. The method of producing a high viscosity index lubricating oil which comprises blending a. solution of petrolatum, a dewaxed lubricating oil distillate and naphtha at a temperature at which the Wax constituents are soluble, chilling the solution rapidly to precipitate the wax in fine crystals and thereby cause the said .distillate to assimilate and hold in solution the constituents of high viscosity and high viscosity index originally occluded by the petrolatum, removing the wax and separating the naphtha.

2. The method of producing a high viscosity index lubricating oil of a predetermined viscosity which comprises blending a petrolatum solution, a dewaxed lubricating oil distillate and naphtha at a temperature at Which the Wax constituents are soluble, there being present in the petrolatum solution bright stock in an amount which with the distillate Will produce an oil having such a viscosity, chilling the solution rapidly to precipitate the Wax in fine crystals and thereby cause the .distillate to assimilate and hold in solution the constituents of high viscosity and high viscosity index originally occluded by the petrolatum, removing the wax and separating the naphtha.

3. The method of producing a high viscosity index lubricating oil which comprises blending a solution of petrolatum, a dewaxed lubricating oil distillate and naphtha at a temperature at which the wax constituents are soluble, chilling the solution rapidly to a temperature Within the range of 42 F. to 70 F. to precipitate the Wax in fine crystals and thereby cause the said distillate to assimilate and hold in solution the constituents of high viscosity and high viscosity index originally occluded by the petrolatum, removing the Wax and separating the diluent naphtha.

4. The method of producing a high Viscosity index lubricating oil Which comprises blending a solution of petrolatum, a dewaxed lubricating oil distillate and naphtha at a temperature at which the Wax constituents are soluble, chilling the solution rapidly and in stages to a temperature within the range of 42 F, to 70 F. to precipitate the wax in iine crystals and thereby cause the said distillate to assimilate and hold in solution the constituents of high viscosity and high viscosity index originally occluded by the petrolatum, removing the Wax and separating the naphtha.

5. The method of producing a high viscosity index lubricating oil of a predetermined viscosity which comprises blending a petrolatum solution, a dewaxed lubricating oil distillate and naphtha at a temperature at which the Wax constituents are soluble, there being present in the petrolatum solution bright stock in an amount which with the said distillate Will produce an oil having such a viscosity, chilling the solution to a temperature below that at Which crystallization of the Wax begins, chiiling the solution further to precipitate a p-ortion of the Wax and to cause the said distillate to assimilate and hold in solution the constituents of high viscosity and high viscosity index originally occluded by the petrolatum, further chilling the solution to precipitate the remainder of the Wax, the rate of chilling being maintained at a value which will precipitate the Wax in fine crystals and thereby prevent occlusion of the said constituents by the Wax, removing the Wax and separating the naphtha.

6. The method of producing a high viscosity index lubricating oil which comprises blending a solution of petrolatum, a deWaxed lubricating oil distillate and naphtha, heating the solution to render soluble the Wax constituents of the blend, chilling the solution to a temperature of the order of 32 F, at a rate of approximately 9.8 F. per hour, chilling the solution further at substantially half the rate as in the initial stage to a temperature of the order of 8 F. to precipitate a portion of the wax and to cause the said distillate to assimilate and hold in solution the constituents of high viscosity and high viscosity index originally occluded by the petrolatum, further chilling the solution at substantially the same rate as in the initial stage to a temperature of the order of 42 F. to precipitate the remainder of the wax, further chilling the solution to a temperature of the order of 58 F. to render insoluble constituents of high molecular Weight and low viscosity index characteristics, removing the Wax and said last mentioned constituents and separating the naphtha.

7. The method of producing a high viscosity index lubricating oil which comprises blending a solution of petrolatum, a dewaxed lubricating oil distillate and naphtha at a temperature between 110 F. and the temperature at which the diluent vaporizes, there being present in the solution bright stock in an amount which with the said distillate will produce an oil of predetermined viscosity, chilling the solution to a temperature of the order of 32 F. at a rate of approximately 9.8 F. per hour, chilling the solution further to a temperature of the order of 8 F. at a rate of approximately 4 F, per hour to precipitate a portion of the Wax and to cause the said distillate to assimilate and hold in solution the constituents of high viscosity and high viscosity index originally occluded by the petrolatum, further chilling the solution to a temperature of the order of 42 F. at a rate of approximately 8.3 F. per hour to precipitate the remain-der of the Wax, further chilling the solution to a temperature of the order of 58 F. at a rate of approximately 2.7 F. per hour to render insoluble constituents of high molecular weight and low viscosity index characteristics, removing the Wax and said last mentioned constituents and separating the naphtha.

8. The method of producing a high viscosity index lubricating oil which comprises blending a solution of petrolatum, a dewaxed lubricating oil distillate and naphtha at a temperature at which the Wax constituents are soluble, chilling the solution rapidly to precipitate the Wax in fine crystals and thereby cause the said distillate to assimilate and hold in solution the constituents of high viscosity and high viscosity index originally occluded by the petrolatum, removing the Wax in the form of a slurry, separating the diluent from the remaining solution, heating the slurry to drive off the naphtha and recover in a distillate oil fractions having high viscosity index characteristics, separating the Wax from the said distillate and adding the latter to the solution of petrolatum, lubricating oil distillate and naphtha which is being treated in the manner described.

9. 'Ihe method of producing a high viscosity index lubricating oil Which comprises blending a solution of petrolatum, dewaxed neutral oil and a naphtha at a temperature at which the Wax constituents are soluble, chilling the solution rapidly to a temperature Within the range of 42 F. to 70 F. to precipitate the Wax in ne crystals andv thereby cause the neutral oil to assimilate and hold in solution the constituents of high viscosity and high viscosity index originally occluded by the petrolatum, removing the wax and separating the naphtha.

LUTHER D. FULTON. JOSEPH M. HINMAN. 

